The international aid group Doctors Without Borders (MSF) said at least 18 people were killed in armed conflict at a U.N. Protection of Civilians site this week, including two South Sudanese staff members attacked in their own homes.

The report regarding the site in Malakal increases the previously reported death toll of seven, which was reported Thursday. MSF said the two staff members killed were workers at one of its hospitals inside the compound.

MSF spokesman Marcus Bachmann reported that medical teams worked through the night to treat some 73 people wounded in the attack, the majority of whom had gunshot wounds. More injured people were arriving at the hospital Friday.

FILE - Displaced people draw water from a hole dug in the ground, in the United Nations camp for displaced people in the capital Juba, South Sudan, Jan. 19, 2016.

The conflict took place between youth from two different ethnic communities - Dinka and Shilluk.

U.N. Mission in South Sudan (UNMISS) spokesperson Ariane Quentire said fighting erupted Wednesday night, with the young people using machetes, guns and other weapons against each other.

The attack forced some 600 people to gather inside the hospital for shelter.

‘Reconciliation and healing’

In a statement Thursday, U.N. Secretary-General Ban Ki-moon condemned the violence and called on all parties to avoid stoking ethnic tensions.

He urged South Sudan's government and rebels to implement the peace deal reached in August, "so that the people of South Sudan can begin a process of reconciliation and healing."

UNMISS spokeswoman Quentire said U.N. military personnel used tear gas to disperse the combatants. She said U.N. peacekeepers also stepped up patrols in and around the camp to contain the situation.

Jacob Nhial, one of the internally displaced persons residing at the U.N. site said the fighters were using machine guns and Kalashnikovs to shoot unarmed civilians.

Nhial said forces of South Sudan's army, the SPLA, are also involved in the shooting.

FILE - Soldiers from the Sudan People's Liberation Army (SPLA) are seen examining a map in Pana Kuach, Unity State, South Sudan.

UNMISS said the attackers were targeting people who are under the protection of the United Nations, a clear violation of international law.

“Attacking U.N. premises and not respecting the sanctity of U.N. premises, compounds and people living in this compound being international or national workers or civilians we are protecting constitutes a war crime," said spokeswoman Quentire.